Precision resistance thermometer bridge, Mueller bridge, metal / plastic / glass, made by Leeds and Northrup Co, Philadelphia, United States of America, c. 1960, used by National Standards Laboratory, CSIRO, Chippendale, New South Wales, Australia, c. 1961-1975, Defence Standards Laboratory, Adelaide, South Australia, c. 1975-1977, and CSIRO, Woodville North, South Australia, c. 1977-1990
The instrument is encased in a grey metal box and has a dark grey metal face into which are set the connectors, dials, thumb wheels, switches and meter. A thermometer (missing) would have been held between the two metal fittings on the face of the unit to enable corrections for room temperature. There are two metal carry handles mounted on the face at the far right and left of the unit.
The thermometer bridge has eight decadic multiplier dials (0-11)x10, x1, x0.1, x0.01, x0.001, x0.0001, x0.00001, x0.000001; a range switch; a glass fronted meter; two large selector switches; five small dials, three thumb wheels and 21 connector posts along the top of the unit and three tap keys at the bottom next to the meter. There are connectors on the left side of the box labelled 'TEMP. CONTROL' and 'READ-OUT'.
Dials, switches, thumb wheel tops, connector tops and the meter housing are black [ebonite]. The cylindrical [ebonite] of each dial and switch is fixed into the centre of a cylinder or disk of metal onto which the position numbers are engraved. Mounted below each dial and switch is a small metal cylindrical position indicator with an engraved fiducial line.
Engraved into the metal surface of the instrument in white is:
'PRECISION RESISTANCE THERMOMETER BRIDGE
LEEDS & NORTHRUP CO.
PHILADELPHIA MADE IN U.S.A.'
Metal sticker attached to side of wood box
'THIS EQUIPMENT IS THE PROPERTY OF
COMMONWEALTH OF AUSTRALIA
This label is engraved with a series of letters and numbers (mostly obscured by the CSIRO sticker) which appears to read
'DSL ?o ??71'
Over this metal sticker is a black dymo label typed